When performing vehicle diagnostics with the aid of a control device installed in a vehicle, safety-relevant data and services, in particular, should be available only after they have been activated by the diagnostic software. A typical example of such a safety-relevant function is training a new immobilizer system or downloading a new software version.
The activation usually takes place using a so-called seed/key method, in which the testing device and the control device share a secret algorithm and key. Such a conventional method usually takes place as follows:    1. A data link is established between the control device and a workshop testing device.    2. The diagnostic software in the testing device initiates a request via the data link to the control device to activate a specific safety-relevant function.    3. The control device responds to the test software with a random value.    4. Since the diagnostic software in the testing device knows the secret algorithm, it is capable of calculating the appropriate response from the random value. The testing device returns this response to the control device.    5. The control device verifies the response from the diagnostic software by calculating the response itself from the random value using the secret algorithm and comparing it with the response transmitted from the testing device.    6. If the response from the test software matches the value calculated in the control device, the safety-relevant function is activated.    7. The control device sends a reply to the diagnostic software as to whether or not the activation has taken place.    8. The diagnostic software and, therefore, the workshop, which carries out such a repair, is now capable of running the activated functions.
Due to statutory provisions, the vehicle manufacturers must also enable independent workshops to carry out motor vehicle repairs and to activate the control device functions necessary therefor, even if the repair includes safety-relevant functions.
For this purpose, the motor vehicle manufacturers usually provide the manufacturers of the testing devices and/or the diagnostic software with a library, which contains the corresponding seed/key algorithms. With the aid of this library, the manufacturers of the testing devices/diagnostic software are capable of also implementing safety-relevant functions and, therefore, of also enabling independent workshops to carry out safety-relevant repairs. Making the libraries available to external parties, in particular independent workshops, poses a certain security risk, however.
One object of the present invention is to provide an improved method and an improved device for activating functions of control devices, in particular motor vehicle control devices, and to thereby provide for an improved control of the access to the functions of the control devices.